Pith Number

pith:B2FBVKLU

pith:2025:B2FBVKLU7SZEJ45YGFFXVLKZ4V

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Can Aha Moments Be Fake? Towards Quantifying Decorative and True Thinking in Chain-of-Thought

Dawn Song, Jiachen Zhao, Weiyan Shi, Yiyou Sun

Most steps in chain-of-thought reasoning have little causal effect on the model's final answer.

arxiv:2510.24941 v4 · 2025-10-28 · cs.LG

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Claims

C1strongest claim

LLMs often interleave between true-thinking steps (which are genuinely used to compute the final output) and decorative-thinking steps (which give the appearance of reasoning but have minimal causal influence). Only a small subset of the total reasoning steps causally drive the model's prediction: e.g., on AIME, only an average of 2.3% of reasoning steps in CoT have a TTS >= 0.7 for Qwen-2.5.

C2weakest assumption

The method used to compute the True Thinking Score isolates the causal contribution of each verbalized step without the intervention itself changing the model's internal computation in unaccounted ways.

C3one line summary

LLMs interleave true causal reasoning steps with decorative ones in CoT, with only ~2.3% of steps having high causal impact on AIME for Qwen-2.5, and a steering direction can force internal use of specific steps.

Formal links

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Cited by

3 papers in Pith

Decoding the Critique Mechanism in Large Reasoning Models

Measuring and curing reasoning rigidity: from decorative chain-of-thought to genuine faithfulness

When Chain-of-Thought Fails, the Solution Hides in the Hidden States

Receipt and verification

First computed	2026-05-28T01:04:32.113170Z
Builder	pith-number-builder-2026-05-17-v1
Signature	Pith Ed25519 (`pith-v1-2026-05`) · public key
Schema	pith-number/v1.0

Canonical hash

0e8a1aa974fcb244f3b8314b7aad59e54689101b444192985e9f1e6b4a7693e1

Aliases

arxiv: 2510.24941 · arxiv_version: 2510.24941v4 · doi: 10.48550/arxiv.2510.24941 · pith_short_12: B2FBVKLU7SZE · pith_short_16: B2FBVKLU7SZEJ45Y · pith_short_8: B2FBVKLU

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Verify this Pith Number yourself

curl -sH 'Accept: application/ld+json' https://pith.science/pith/B2FBVKLU7SZEJ45YGFFXVLKZ4V \
  | jq -c '.canonical_record' \
  | python3 -c "import sys,json,hashlib; b=json.dumps(json.loads(sys.stdin.read()), sort_keys=True, separators=(',',':'), ensure_ascii=False).encode(); print(hashlib.sha256(b).hexdigest())"
# expect: 0e8a1aa974fcb244f3b8314b7aad59e54689101b444192985e9f1e6b4a7693e1

Canonical record JSON

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    "abstract_canon_sha256": "509576d802b9d6e23184949c52799429f5065cdd6d57279845f3e0fa528a14d5",
    "cross_cats_sorted": [],
    "license": "http://creativecommons.org/licenses/by/4.0/",
    "primary_cat": "cs.LG",
    "submitted_at": "2025-10-28T20:14:02Z",
    "title_canon_sha256": "1b1b480ee2b97b21969d215ec2f3c34fd021bab84275eeda898bdb72974ce35b"
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  "source": {
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    "kind": "arxiv",
    "version": 4
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